The present invention relates to a portable surface inspector for surface inspection of a flat body, especially a lapping plate.
A lapping plate used for precise processing of brittle materials, the curved surface of a GMR head, etc. has a curved or straight processing surface provided with a fine spiral groove. The processing surface must be kept in good condition macroscopically and microscopically so as to maintain high processing accuracy. The processing surface must be accurately inspected macroscopically and microscopically so as to keep it in good condition macroscopically and microscopically.
Surface inspection of the processing surface of a lapping plate has been carried out with the following inspecting apparatuses.
A. Inspection of macroscopic shape of processing surface such as flatness, sphericity, etc.
a. Span gauge
b. Three-coordinate measuring machine
c. Comparator, Dial gauge
B. Inspection of microscopic shape of processing surface such as groove shape, etc.
a. Surface roughness tester
b. Scanning electron microscope
There have been the following problems with the conventional inspecting apparatuses.
Span gauge: Local deformation is liable to be overlooked because a span gauge carries out point inspection.
Three-coordinate measuring machine, Comparator, Dial gauge: The processing surface of a lapping plate detached from the lapping machine can be inspected but the processing surface of a lapping plate attached to the lapping machine cannot be inspected.
Surface roughness tester: Spherical surfaces are hard to inspect because the inspectable range in the direction of the Z-axis (axis extending in the direction of the thickness of a flat body) is less than 1 mm.
Scanning electron microscope: Wide surfaces are hard to inspect because the inspection speed is very low.
Contact type surface inspectors such as the span gauge, three coordinate measuring machine, surface roughness tester, comparator, etc. cannot carry out accurate inspection of the processing surface of a lapping plate made of soft metal such as tin and are liable to damage the processing surface.
An object of the present invention is to provide a portable surface inspector which can inspect easily and accurately the macroscopic shape and the microscopic shape of the processing surface of a lapping plate attached to a lapping machine.
Another object of the present invention is to provide a portable surface inspector which can inspect easily and accurately the macroscopic shape and the microscopic shape of the surface of a flat body.
In accordance with the present invention, there is provided a portable surface inspector comprising a straight guide rail, a table engaging the guide rail to be movable along the guide rail, a stage engaging the table to be movable in the direction of a transverse axis crossing at right angles with the longitudinal axis of the guide rail, a non-contact displacement sensor fixed to the stage, a first driving means for driving the table, a first coordinate detecting means for detecting the longitudinal axis coordinate of the non-contact displacement sensor, a second driving means for driving the stage, a second coordinate detecting means for detecting the transverse axis coordinate of the non-contact displacement sensor, and a coordinate correcting means for correcting the transverse axis coordinate of the non-contact displacement sensor with the deflection in the direction of the transverse axis of the guide rail.
According to a preferred embodiment of the present invention, the portable surface inspector further comprises a constant distance keeping means for keeping the distance in the direction of the transverse axis between the non-contact displacement sensor and the inspected surface constant.
According to another preferred embodiment of the present invention, the non-contact displacement sensor is a laser sensor.
According to another preferred embodiment of the present invention, the portable surface inspector further comprises an air bearing supporting the table.
According to another preferred embodiment of the present invention, the guide rail is made of ceramic.
According to another preferred embodiment of the present invention, the portable surface inspector further comprises a measured surface shape data storing means and a measured surface data analyzing means.
According to another preferred embodiment of the present invention, the portable surface inspector further comprises an initial surface shape data storing means for storing the initial surface shape data of the inspected surface and a wear detecting means for detecting the wear of the inspected surface based on the initial surface shape data and the measured surface shape data.
According to another preferred embodiment of the present invention, the portable surface inspector further comprises a first warning means for displaying a warning when the wear of the inspected surface exceeds a permissible level.
According to another preferred embodiment of the present invention, the portable surface inspector further comprises a second warning means for displaying a warning when increment of the wear from that at the last inspection exceeds a permissible level.
According to another preferred embodiment of the present invention, the portable surface inspector further comprises a support member for the guide rail and a support member locating means for locating the support member relative to the surface to be inspected.
According to another preferred embodiment of the present invention, the guide rail is connected to the support member to be detachable.
According to another preferred embodiment of the present invention, the support member is provided with a plurality of legs of adjustable length.
According to another preferred embodiment of the present invention, the transverse axis coordinate of the non-contact displacement sensor at the home position is marked on the support member.
According to another preferred embodiment of the present invention, the transverse axis coordinate of the non-contact displacement sensor at the home position is marked on the support member locating means.
In accordance with the present invention, there is provided a method for inspecting the surface shape of a flat body comprising the steps of:
moving a non-contact displacement sensor movable along a straight guide rail to a first position in the direction of the longitudinal axis of the guide rail;
moving the non-contact displacement sensor to a second position in the direction of a transverse axis crossing at right angles with the longitudinal axis of the guide rail;
measuring the distance in the direction of the transverse axis between the non-contact displacement sensor and the surface to be inspected;
detecting the longitudinal axis coordinate of the first position of the non-contact displacement sensor;
detecting the transverse axis coordinate of the second position of the non-contact displacement sensor;
calculating the transverse axis coordinate of the inspected point of the inspected surface based on the distance in the direction of the transverse axis between the non-contact displacement sensor and the inspected surface, the transverse axis coordinate of the second position of the non-contact displacement sensor, and a correction value for correcting the transverse axis coordinate of the second position of the non-contact displacement sensor based on the deflection of the guide rail in the direction of the transverse axis; and
carrying out the above steps at various different first positions of the non-contact displacement sensor.
According to a preferred embodiment of the present invention, the distance in the direction of the transverse axis between the non-contact displacement sensor and the surface to be inspected is kept constant.
According to another preferred embodiment of the present invention, the method for inspecting the surface shape of a flat body further comprises the steps of:
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points; and
displaying the radius R of the calculated circular arc.
According to another preferred embodiment of the present invention, the method for inspecting the surface shape of a flat body further comprises the steps of:
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points;
calculating differences xcex94R in the direction of the transverse axis between the calculated circular arc and the measured points; and
displaying the differences xcex94R.
According to another preferred embodiment of the present invention, the method for inspecting the surface shape of a flat body further comprises the steps of:
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points;
calculating differences xcex94R in the direction of the transverse axis between the calculated circular arc and the measured points;
calculating the difference xcex94H between the maximum xcex94R and the minimum xcex94R; and
displaying the difference xcex94H.
According to another preferred embodiment of the present invention, the inspected surface is symmetrical around a rotation axis, and the method for inspecting the surface shape of a flat body further comprises the steps of:
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points over a diameter of the inspected surface;
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points over a radius of the inspected surface; and
displaying the radius R of the circular arc calculated based on the measured points over the diameter and the radius R of the circular arc calculated based on the measured points over the radius.
According to another preferred embodiment of the present invention, the inspected surface is symmetrical around a rotation axis, and the method for inspecting the surface shape of a flat body further comprises the steps of:
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points over a diameter of the inspected surface;
calculating the circular arc of the inspected surface based on the measured longitudinal axis coordinates and the transverse axis coordinates of a plurality of measured points over a radius of the inspected surface; and
displaying the difference between the radius R of the circular arc calculated based on the measured points over the diameter and the radius R of the circular arc calculated based on the measured points over the radius.
Further objects, features and advantages of the present invention will become apparent from the Detailed Description of the Preferred Embodiments when read in conjunction with the accompanying drawings.